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Authorities expand their search for more remains after eight bodies are discovered on a remote stretch of Long Island beach. (Published Wednesday, Apr 6, 2011)

Updated at 4:15 PM EST on Friday, Apr 8, 2011

Suffolk police are wrapping up their exhaustive search for remains along the remote Long Island beachfront where eight bodies have been found in a case that could be the work of a serial killer.

After a four-day search involving cadaver dogs, police cadets and ladder trucks, Suffolk is calling off the intensive effort. But across the county border in Nassau County, police will begin combing a new area for bodies.

Shannan Gilbert's Disappearance: A Timeline

Shannan Gilbert was last seen alive on May 1. Authorities have uncovered eight bodies so far in their search for her, and suspect she may be the victim of a serial killer. (Published Wednesday, Apr 6, 2011)

Suffolk Police Commissioner Richard Dormer said that "it is possible we missed something, and as I said, we're gonna be back here again. We're not giving up."

Police have erected a flashing sign nearby, asking for tips to help crack the case.

The sign reads: "Gilgo Murders -- Cash for Tips" and includes the Crime Stoppers number, 1-800-244-TIPS.

In all, eight bodies have been found along the remote swath of coastland, mostly in thick underbrush.

Four were found last year as police searched for a woman who had gone missing nearby, and four have been found in the last week.

Police said today that no suspect has been identified in the slaying of the first four victims.

The bodies of the first four, discovered in December, had all worked as sex workers. The woman who went missing in May of last year, Shannan Gilbert, was also a prostitute; she has not been found.

Gilbert's sister told NBC New York that the family is discouraged.

"It's really frustrating and upsetting," Sherre Gilbert said. "Why has it taken so long to find her?"

The recent findings have not been officially linked to the earlier discoveries, but police have said they suspect a serial killer may be at work.

NBC New York on Thursday spoke to Gus Coletti, who may have been one of the last people to see Gilbert before she vanished. She has not been seen since she visited a client in nearby Oak Beach.

Coletti, who lives in the gated community, has said a woman believed to be Gilbert came to his door around 4:45 a.m. on May 1, pleading for help. When he tried to call police, she fled.

He said he is haunted by the thought that he did not help her.

"it still bothers me to think that I could have done more to help the girl," said Coletti.

She was last seen running toward the water.

The hunt for remains is expected to shift into Nassau County in coming days.

Officials from the Nassau County Police Department and the New York State Police will be searching west along Ocean Parkway, authorities said.

State troopers, Nassau officers and state parks police will work from the Nassau-Suffolk border to the Jones Beach water tower.